Agreement
by DeadlyAnimeFreak
Summary: AU- Disappointed by the response to who he really is, Rin decides to make a deal with Satan. Will he be able to accomplish his end? Or will the world crumble beneath Satan's feet?
1. Chapter 1

Disclaimer: I do not own Ao no Exorcist

A/N: This is my first time every writing a fanfiction so I am very excited. Since I am new, I am inexperienced and would very much appreciate your feedback. I also apologize if I don't get the character's personalities spot on but I do plan to have Rin change. I have been craving for a dark and colder Rin, so I hope you guys will continue to read. Also just a heads up, I am going to have some OC within my story.

~Hope you guys enjoy~

The overly large hallway was completely deserted not a single person passed me by. Although, it was three in the morning. The moon was still shining with radiance as the sun slept for a few more hours. I had tried countless times to fall asleep, but my mind kept wandering. A day had gone by since everyone found out I was Satan's son. The images of Shiemi and Suguro's terrified faces were engraved in my mind, and their words still harshly ringed in my ears. I still remember being forced to kneel before the Order, and how they were wary of my presence. Savior? Weapon? Demon Lord? I am no Savior, nor am I a weapon and I am definitely not a Demon Lord. They decided what I was from the very beginning without getting to know me. I didn't ask to be born this way and I haven't done anything wrong. My thoughts were faced with more questions. I could feel my chest tightening with every breath, but a clearing of a throat snapped me back to reality. Mephisto sat behind his large red wood desk. His hands folded together as he rested his chin upon them. I must have unconsciously walked to Mephisto without even knowing it.

"What brings you here this late at night, Rin," he questioned while wearing a yukata that had a floral print. It was beautifully painted with a mixture of pink and white.

I hesitated at first but the image of my blue flames scorching through the forest as if it was alive, made me come to a realization. "I want to go to Gehenna," I said while clutching Kurikara.

"Gehenna?….Hahaha," Mephisto bursted out laughing at my response. "Interesting. Why do you want to go to Gehenna?" he asked while trying to catch his breath.

"I am Satan's son there is no denying that, but Kuro who is a pure demon cried for my dad. My father raised me as his own, so why can't we just all get along?...I want to learn more about Gehenna." My grasp on Kurikara grew tighter. I could feel Kuro rub against my leg in reassurance that he was by my side. I was in such a confused state I didn't notice Kuro had followed me until now.

Mephisto rose a brow and has a large grin plastered on his face. "Yukio won't like this idea one bit," he stated as he arose from his seat while intensely staring at me.

I stared back at him with the same intensity, "Yukio doesn't understand." My voice was stern.

"Alright," Mephisto's eyes gleamed with enjoyment, "Let's get you to Gehenna." His grin was now revealing his teeth.

"R-Really," I asked surprised to his agreement.

"Sure, why not. It will be entertaining," he snapped his figures and a small pink polka dotted box appeared in his hand. Mephisto opened the box and two large scaly hands with long sharp nails pulled Kuro and I inside. My mind and senses were going numb, but I swear I heard Mephisto say, "What a troublesome little brother."


	2. Chapter 2

**A/N: Hello everyone!**

**I want to thank everyone who commented. I literally couldn't stop smiling. :D**

**I really enjoy the feedback, so don't be afraid to tell me what you think. I plan to post every other week on Mondays, so I hope you guys continue to read.**

**Beta: ShyReader18**

**Disclaimer: I don't own Ao no Exorcist**

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The touch of something moist pressing up against my face startled me. My eyes flashed open and I saw Kuro licking me. A sign of relief escaped my lips in response to Kuro's presence.

"Rin are you ok?" Kuro's voice shook.

I sat up while trying to regain feeling throughout by body. A small note was pinned to a black cloak that draped over my legs. It was Mephisto.

_I generously placed a choker on you that limit your power. Once the collar is removed, your true self will be revealed and you won't be able to go back._

_ Mephisto ^.^_

I remember someone telling me my flames were in Gehenna and my body in Assiah. If this choker is removed then I really won't be human. I traced my fingers on my neck feeling the velvet material with crosses stitched in it.

"I'm fi-"I broke off. A red sun burned majestically in the dark sky giving off a sunset feel. There were no stars, but across from the sun were shattered rocks floating aimlessly. The color and light produced resembled that of a moon. Beneath the unearthly sky was a mountain with buildings emended within it.

"This is Gehenna? It looks like True Cross." I said in disbelief. I couldn't see the conditions the city was in because I was on the outskirts of the city's walls. The stone walls were enormous.

Kuro purred with excitement, "This is the Palace in Gehenna and it's four times the size of True Cross."

Well that explained were Mephisto got his decorating ideas. I could feel myself mimicking Kuro. I was excited too, but I wasn't sure why.

"Let's go" was all I could say.

…..-

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Yukio

This morning the sound of the alarm clock annoyingly buzzing in my ears made me get up. Exhausted from everything, I slept like the dead last night. I got up like usual but I didn't see Rin sleeping in his bed. I searched through the whole building but found nothing. Not even Kuro. It was very unsettling. Day classes were cancelled today, but I still had night classes. Rin probably needed space to think, so he most likely went for a walk. I am always on Rin, so I felt I could give him some time alone just this once. He needed it after the greeting he got from everybody yesterday. I walked into the classroom and the atmosphere was very intense. Just as I began to unpack the door flew across the room.

"Where's Rin?" Shura shouts. She glared at the class who stiffened at the mere mentioning of Rin.

"He should have been with you" I sighed.

"Well he's not. I have been waiting an hour for that bastard," she growled. I knew she was serious and what's weird was that I haven't seen him at all today. From the corner of my eye, I could see the ex-wires lose their color.

"Sorry but today's class is cancelled!" I rushed out the door. The one person who would know where my brother is would be Mephisto. I could hear Shura following closely behind me. I'm sure she was thinking the same thing.

Without a second thought I barged into Mephisto's office, "Where is Rin?"

"And don't try to avoid the question either!" Shura added.

"Rin? Weren't you supposed to babysit him?" Mephisto grinned as he sat behind his desk with his hands folded together.

"Shut up and tell us where he is!" Shura pulled out Kirigakure and pointed the sharp blade at Mephisto.

Mephisto didn't look surprised but instead pleased. "You're rather attached to Rin, aren't you?" His smile didn't fade.

"Where is my brother?" I too pointed my gun at Mephisto showing him that I meant business.

"I wonder," he said almost as if he was taunting us but his tone quickly changed. "I will look in every nook and cranny." He stood up and bowed before me.

I dropped my arm to my side and put my gun away. Shura did the same. "I will also look for him," I said and Mephisto just nodded in agreement. We were just about to leave when Shura grabbed me by the shoulder and whispered in my ear, "I don't trust him."


	3. Chapter 3

**A/N: **_I'm sorry I have been gone for so long but a family emergency happen and I had to dedicate my time to them. I'm back now and plan to post every other week like I promised ^.^ Rin has changed a great deal and you will get to know about his time Gehenna throughout the story. _Also I hope you like Izaki and Aciel my original characters xD

**Beta: **_ShyReader18_

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**3 year Time Skip**

Mephisto stared out the window, watching the ominous clouds build above the academy. It looked as if they were signaling a storm was brewing. With a clear of his throat Mephisto sat behind his desk as he slouched in his chair. "It's been awhile since we talked little brother," he said in a sarcastic tone while he stared intensely into the shadows.

A pair of cold, blue eyes stared back at him menacingly. "You know why I'm here, so I don't have time to waste on your meaningless games," he stated, his voice chilling. A pair of golden and red eyes were now visible in the shadow reflecting Mephisto's tension.

A smirk appeared on Mephisto's face in response. " It seems that not just your appearance has changed but also your attitude, Rin." Mephisto shifted his position in his chair, " Yes, I know why you're here and that time is against you...so..I called in some help," he said cheerfully.

The sound of multiple footsteps echoed through the halls and stopped in front of the door. Rin's eyes widened." You Bastard!" he growled. The door creaked open and entered the ex-wires, however, they were no longer ex-wires but experienced exorcist. They grew in rank.

**Yukio's POV**

I've been on edge all day. Mephisto wanted the whole team to assemble out of nowhere. I'm not sure if this has anything to do with Rin or not but….I can't stop thinking that when I wake up in the morning he will be there looking at me with a stupid grin. It's been 3 years and I've searched and searched for him. The higher ups put a price on his head in fear since they believe that he is our greatest adversary. They put all of Rin's contacts into a group and called us the Executioners. We are to find Rin and execute him.

My thoughts just kept going back to Rin and before I knew it, I was in front of Mephisto's door. "Get ready everyone," I whispered to the team before opening the door.

Mephisto was sitting behind his desk in a really good mood. It was disturbing. I felt unfamiliar gazes and looked to see who the guests were. They were in the shadows so I couldn't tell who they were until a cloud passed over letting the sun give me a glimpse. It's weak rays shined through the window revealing….Rin! It was Rin standing there...His hair grew longer. It went to his waist and his face was so stern and cold. I started to doubt he was Rin at all until he spoke. "I don't need any help from them, they will only slow me down." Rin's voice was cold.

"Where..Where were you? Why did you leave?!" I yelled with so much anger. He had me worried! He didn't even try to contact me! He ignored me completely. More light shined through and I could see Rin better. He wore a long, military like jacket with black pants that were tucked inside his boots. His sword was at his side and that's when I noticed two horns on his head. "What are you?" I muttered in disbelief.

Two unfamiliar demons that stood next to Rin approached me and I drew out my gun on instincts. "So this is the Prince's younger brother. He looks weak," laughed the demon with golden eyes. "I could care less who he is but he needs to know his place," said the demon with red eyes in a threatening tone. They were both in military attire almost similar to Rin's.

"Izaki! Aciel! Enough." Rin said sternly.

"Now, now. Everyone here are friends. The exorcists and the demon army have a common goal," said Mephisto with a clap of his hands.

Demon Army? Why would Rin be working with the demons? What just happen in the past 3 years? I could feel Shura and the rest off the team freeze up.


	4. Reunited

A/N: I apologize for being two days late! Some baby mamma drama was going on! Hahaha I'm just kidding, it was just school stuff I had to take care of ^^

Disclaimer: I do not own Ao no Exorcist

Beta: ShyReader18

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**~FlashBack Rin's POV~**

**I sat emotionlessly on a chair in one of the cells within the palace. I could feel my body growing cold, like all the warmth fled in an instant. I stared at the young boy that laid in a puddle of his own blood. His golden hair stained with red. He was so thin. Like his body would break after a single breath. **

"**There was nothing you could do….he was already dying", said Aciel as he looked at me with sorrowful eyes. It reminded me of my weakness. I was too powerless to protect him.**

**Izaki covered the body with a black sheet. "He was a fool to think humans were beautiful creatures…..that kind of thinking got him killed. He was an idiot, " Izaki growled with his black hair covering his eyes. I knew he was wounded as well. That's when I heard a deep laughter and it was none other than Satan. I couldn't see him, but I knew his voice.**

"**Are you sure you want to continue with our bargain? It's not too late to back out" he continued to laugh in amusement, "only if we emerge Assiah and Gehenna together will there be union", his voice slowly mellowed out.**

"**I will continue. Your way will kill everything", I said more to myself than to Satan. **

~In the present Rin's POV~

"A common goal?", questioned Yukio.

"Yes. To save the world! Doesn't that sound exciting?" Mephisto chuckled, "I mean Rin did give up being human to make a deal with Satan after all", he looked at me with a mischievous smile.

"Mephisto, if you don't quit it, I'll kill you," I snarled.

"Oh-ho ho ho! Scary," he said like he was pleased. " We do have a common goal. We want to stop this pointless fighting, don't we?", he asked as he closely watched our reactions.

"You have some nerve! Common goal or not Rin will have to stand before the council," Shura shouted as her body shook with anger.

"Of course he will. We also have to make our offer as well,"Mephisto slid out from his chair and headed for the exit. "Shall we go then?" he asked as he held the door open.

"I don't know what you're planning but the council won't agree," Suguro added as he passed me to leave. Shemi and the others wouldn't even look at me in the eyes. They were just as scared as they were back then.

I took a deep breath, "We will be right next to you at all times," whispered Aciel to put my mind at ease. However, I knew the path I chose would be rocky.

"Just behind this door is our destination," grinned Mephisto. He didn't seem at all worried, so I knew he was cooking up some sort of plan. It's still unclear whether he works with the demons or sides with the humans, but it doesn't really matter. As long as he's useful. He creeked the door open and sure enough a long hallway stretched out and at the end were double doors. I knew the council was waiting. I dawdled down the hall. What was only minutes, felt like hours. The double doors opened, and I received the dirtiest look from Angel.

"Mephisto, what is this!?" questioned a man that sat high in one of the golden chairs.

"The Prince of Gehenna of course," replied Mephisto.

The council roared with chatter and I could see from the corner of my eye jaws dropping from my old friends. "What is the meaning of this!?" shouted a woman.

I walked to the center of the room near Mephisto, and I could feel Izaki and Aciel closely behind me. "Like he said, I'm the Prince of Gehenna and I've come to make an offer."

The whole time I could feel Yukio's gaze.


	5. Prince of Gehenna

**A/N:** My finals are almost over *cries tears of joy* so I made this chapter slightly longer ^^

**Disclaimer: **I don't own Ao no Exorcist

**Beta:** ShyReader18

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Rin's POV

The three Supreme Advisors had their usual white expensive looking hoods hiding their faces. Two males, one younger than the other and a single female were sitting beneath a golden chandelier brightly shining.

"Offer? You're in no position to be making an offer! We should have you both killed!" shouted the older male with a white beard sneaking out from under his hood.

"Killing the Prince of Gehenna would anger Satan and motivate him to act more aggressively," responded Mephisto.

"What's the content of the offer?" questioned the female.

Mephisto smiled. "I'm glad you asked," he said as he looked at me.

I climbed the golden stairs to the podium as Aciel and Izaki waited at the bottom of the steps for me.

Noticing the shadowy figures watching as they hid behind the elegant deep red curtains from the balcony, I let out a sigh just before speaking. "I have accepted my heritage and also what I should inherit. I think in would be in both of our interest if Satan left his throne and who better to remove him then his son. I will replace my father and make a world where Assiah and Gehenna never touch. Will you aid me on my quest?"

"Why should we trust you? The order had agreed to Lord Pheles wager and what do we find, Satan's spawn living in Gehenna," said the younger man.

"Because I have gained Satan's trust and studied under him personally for three years as well as created my own private army,",I replied.

The room grew silent and the council whispered among themselves. I crossed my arms and knew at that moment they would accept. I'm not sure if it was to keep me closer and watch my every move until they found my weakness. They are unsure of my strength and ties at the moment and it would be a wise decision to study me further or would they just out of curiosity. Whatever the case might be I knew that I would be on tight surveillance. I would have to make sure that my true mission stay a secret from the Order.

"Alright Mephisto and Prince of Gehenna. We will agree to this deal, however, we do have conditions. The Execution squad as well as Shura and Angel will be housed with you and your friends. Remember this Prince, if we find you in the least bit suspicious, we will not hesitate to kill you."

With that said we were sent to the abandoned boys dormitory. Everyone went to their rooms and started unpacking. Yuko blocked me from entering the room with Aciel and Izaki.

"You will be sleeping in your old bedroom where I can keep an eye on you," he glared.

"Have it your way then," I responded while walking to my room.

Yuko was furious at me that was made clear from the very beginning. However, he seems like he's been doing well. He doesn't look exhausted but more determined than ever. I opened the door and saw that my stuff hasn't been moved but it looks like it has been regularly dusted and the sheets look new. He must have waited for me.

"Where have you been? Why do you look like that?" he asked as he closed the door behind him.

"I've been in Gehenna."

"I know that! But where? You said you studied under Satan!" he clenched his fist as he spoke,"The demon who killed father…...you called that demon your father!"

"Yuko, I'm not a fool. I couldn't beat Satan as I was, I needed an army and strength. He is my biological father after all."

"What happen to you? Rin would never have said such things. He would have tried killing Satan no matter what. Fujimoto was his only father!"

"I guess I grew up, isn't that what you wanted?" I laid down on my bed and turned my back on Yukio. Kuro climbed out of my jacket and curled up right next to me. All I heard was the slamming of the door and Yukio's foot steps. He knew he wouldn't get any information out of me.

**~Flashback, Palace of Gehenna~**

**As I drew closer and closer to the Palace, the stench of rotting flesh stung my nostrils. I scrunched up my nose in disgust. The walls looked as if they were molding and the smell it admitted was repulsive. It smelt like sewage; I gaged in response. There was no gates sealing off the entrance just a large gaping hole.**

"**Follow me Rin," Kuro said as he leaped off my shoulder and walked in front of me. **

**I tugged on the hood of my cloak to better conceal my face. When I looked down, I noticed I was walking on garbage. The sewage smell was coming from the filth on the floor. Tons of small buildings were cluttered together and stationed on all the mountains of garbage. With every step, I could feel the slime and hear the crunches of me crushing the trash. Kuro didn't seem at all bother by this. He just happily walked on ahead of me. It was crowded with demons and loud with chatter and laughter. I was nervous that I would lose sight of Kuro but he slowed down his pace for me to catch up and dodge the swarms of demons. Coal Tar infested the demons and the sky. It looked like dark clouds were looming above us but it was just numerous Coal Tar swarming together. One demon about 7ft tall with an overly muscular build bumped into me. He had one toned arm and the other looked like a tentacle. He was oozing a green slime from his mouth and seemed to have no teeth. His nose was smashed in his distorted face and his bald head was covered with small horns.**

"**Watch where you're going," he spat.**

**His green slobber rushing at me and stuck to my cloak. He pissed me off, but I bit my tongue not wanting to draw attention to myself. Instead, I slipped back into the crowd and ignored him. Kuro seemed relieved that I did so. As we got deeper and deeper into the city, the mountain with building embedded in it seemed cleaner. **

"**Watch it Rin!" Kuro shouted. **

**His warning took me by surprise and shook me up a little. I looked down at my feet again and almost walked over a cliff. The mountain was in a giant pit surrounded by a blue lava and flames shot up so high that it reached the edge where I stood. **

"**We have to go down here," Kuro said as he showed me a narrow steep pathway that went down the cliff and to an arch like door with eyes and unknown clumps of dark grey slime covering it.**

**We started on the path and garbage was scattered about with maggots crawling in and out of the trash. The loud chatter from the city grew fainter, only the bubbling of the lava could be heard. Once again, flames scorched up. Out of curiousity, I stretched out my hand and placed it within the fire. I felt nothing. Just a heat resonating within me. Just like my flames.**

"**Those are Satan's flames," muttered Kuro as he sat and watched me.**

"**Satan's flames," I mumbled. **

**After journeying through the long pathway we came to the unusual gate that closely resembled the gate that tried to suck me up last time. The six eyes twitched and it spoke,"Who are you? You touched the flames," it's voice a mixture of a child and a demonic voice. **

"**Let me through!" I glared only revealing my eyes.**

"**Watch your tongue boy," the gate snarled back. **

**Suddenly its eyes grew wide with fear. "Walk into my mouth," it said as a mouth emerged from the grey odd substances and opened rolling its tongue out like a rug. It's sharp teeth were dripping with worms. **

"**What the hell? Why would I-" I broke off. **

**Kuro nudged my leg, "It's ok Rin."**

**Kuro looked up at me. "Alright. I understand," I grumbled beneath my breath. **

**Once we were in, it's mouth closed leaving us in complete darkness. I followed the sound of Kuro's paws hitting the moist tongue as it made splashing noises from the saliva. **


End file.
